Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 181721
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1121 AM CST Thu Jan 18 2018

.UPDATE...
Issued at 1121 AM CST Thu Jan 18 2018

Latest satellite imagery and webcams continues to show a cirrus
shield sliding across western and central ND. Some solar
translucency at times, so will continue with a cloudy to mostly
cloudy sky condition in the sky grids. High temperatures tricky
due to limited solar insolation, but warm air advection continues
today, and already across southwestern ND, temperatures are in the
mid 30s. So, thinking is current temperatures will steadily trend
toward the lower 40s southwest, with 30s elsewhere.

As for the light wintry mix northwest and north central tonight,
high resolution model solutions are changing hourly, both on
location, amounts, and coverage, so low confidence on POP`s at
this time. About half of the 12z global models favor northwest
and far north central ND later tonight as the targeted areas for a
light wintry mix; however, exact location and amounts differ for
each. This again favors low POP`s. The previous forecast had a
slight chance northwest and north central and this seems to best
convey the message from the latest guidance. Will continue to
advertise this in the AFD and HWO, and watch for any changes as
the latest data comes in. For now, no changes to previous
thoughts/discussions at this time.

UPDATE Issued at 805 AM CST Thu Jan 18 2018

Per previous forecast discussion(s), warm air advection continues
this morning and today. Latest satellite imagery indicative of
this as a large canopy of cirrus from central Montana into western
North Dakota continues to move east. Partly to mostly cloudy sky
conditions and mild today is on track and no changes with this
update.

UPDATE Issued at 623 AM CST Thu Jan 18 2018

Considerable high level cloudiness spilling into western ND at
this time. Bumped up sky cover for today. Increased clouds may
hamper temperatures somewhat, but most areas are starting out
much warmer than yesterday. No changes to temperatures other than
populating latest obs and interpolating to mid-morning values.

&&

.SHORT TERM...(Today and tonight)
Issued at 329 AM CST Thu Jan 18 2018

Highlights in the short term include mild conditions today and
tonight, with a small chance of a wintry mix late tonight north.

Currently, a small scale low was over the borders of
Manitoba/Ontario/Minnesota, with an upper level ridge over the
Rockies ahead of a large eastern Pacific upper level low off the
coast of British Columbia.

Today and tonight the small scale low moves east as the Rockies
ridge moves east across the Dakotas and the large eastern Pacific
low moves onshore in BC as it digs and develops into a longwave
trough along the west coast of the US.

Today will be another mild January day as the mid level thermal
ridge moves east across our region. Water vapor satellite pics show
the mid and high level clouds associated with this thermal ridge
spreading east out of the Rockies and Front Range into the western
plains. Expecting these clouds to dominate today with partly to
mostly cloudy conditions. Lighter westerly winds today, so should
not have the drifting snow concerns like yesterday. We should still
be quite mild with highs from the lower 30s in the Turtle Mountains
to the low/mid 40s southwest. Thus more melting should occur. Any
wet roadways will likely freeze tonight with overnight lows in the
mid to upper 20s expected.

The main concern is a chance of light precipitation late tonight
across northern North Dakota. As the thermal ridge continues moving
east, some of the global models develop an area of light
precipitation as a weak cold front moves southeast across the state.
Temperature profiles suggest a mix of rain, freezing rain, or sleet
possible. Confidence is low regarding occurrence and areal coverage
of this short-lived event, so kept only a slight chance mention.

.LONG TERM...(Friday through Wednesday)
Issued at 329 AM CST Thu Jan 18 2018

The highlight in the long term is a slight chance of a light wintry
mix possible along the South Dakota border Saturday afternoon,
followed by chances of light snow Saturday night and Sunday south
central into the James River Valley.

By Friday upper level southwesterly flow has become well established
from the base of the west coast trough across the Rockies into
central Canada. One more mild and dry day in the offing Friday for
North Dakota. Look for high temperatures in the mid 30s to lower 40s
and lows Friday night from the upper teens to lower 20s.

The longwave trough digs as it moves onshore into California,
setting up southwest flow aloft upstream across the Rockies to the
Northern Plains by Saturday. The global models depict the leading
edge of upper level energy impulses emanating from the base of the
trough reaching western South Dakota and to the border of North
Dakota. The consensus of the models suggests a slight chance of
precipitation along the southern tier of central North Dakota
Saturday afternoon. Surface temperatures are expected to be in the
mid to upper 30s in this area, with temperature profiles indicating
precip type could be rain or snow.

Saturday night and Sunday the trough moves east across the US
Rockies and the base of the trough becomes dominant as it moves into
the southern plains. An associated surface low develops in response
over the southern plains Saturday night and begins lifting northeast
towards Iowa by Sunday afternoon, reaching southern MN/WI by
daybreak Monday morning. Southern North Dakota (far south central
through the James Valley and east) will be on the northwestern
fringe of the precipitation associated with this storm system.
Northerly winds will develop over the Dakotas as the system deepens,
pulling colder air south from Canada. Thus any precipitation will be
in the form of snow for North Dakota. Light snow is expected across
far south central ND into the James Valley Saturday night through
Sunday night. At this time the consensus of the global models
suggests snow amounts of 1 to 3 inches possible in the southern ND
counties south of Jamestown, namely in the McIntosh, LaMoure, and
Dickey county area (towns of Ashley, Lamoure, Ellendale, Oakes).

A progressive pattern continues beyond Sunday, but details on the
timing of any one system remains too uncertain at this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1121 AM CST Thu Jan 18 2018

Cirrus shield sliding across western/central ND with a resultant
bkn/ovc 20kft cloud base. This will be maintained through early
evening. VFR cigs/vsbys will continue, but cigs will begin to
lower at KISN/KMOT after 06z Friday, as a slight chance of a
wintry mix develops between 06z-15z Friday. Confidence remains
too low on location and duration at any one terminal, thus will
not mention any vcsh at this time.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...KS
SHORT TERM...JV
LONG TERM...JV
AVIATION...KS



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